I am trying to measure GPP. I am using GIMMS NDVI3g data.When I was process data with Matlab, The NDVI values is displaying a range much beyond the limits ( above 10000 and below -3000). What could be the problem?
Any help is highly appreciated.
Sara Abdali, I agree with the previous answer by Yolandi Ernst
It is simply a matter of how the dataset is packaged. In case of GIMMS AVHRR NDVI3g, it is delivered as a 16-bit signed integer product with a scale factor of 10000. So multiplying by 0.0001 should give you the ideal NDVI range (-1 to 1). Also pay attention to the 'Flag Values' as described in the attached link below or the metadata file associated with the dataset.
https://nex.nasa.gov/nex/projects/1349/wiki/general_data_description_and_access/
Hi Sara. It should be a simple conversion as the data may be stored in different formats. If the data ranges between 10000 and -3000 it can be divided by 10000 to give you the normal range of NDVI values. Usually when you download specific data there is a file or document that explains the conversion formula. Hope this helps.
Sara Abdali, I agree with the previous answer by Yolandi Ernst
It is simply a matter of how the dataset is packaged. In case of GIMMS AVHRR NDVI3g, it is delivered as a 16-bit signed integer product with a scale factor of 10000. So multiplying by 0.0001 should give you the ideal NDVI range (-1 to 1). Also pay attention to the 'Flag Values' as described in the attached link below or the metadata file associated with the dataset.
https://nex.nasa.gov/nex/projects/1349/wiki/general_data_description_and_access/
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